Amplifying and reproducing system



May 27, 1930. L. F. DOUGLASS AMPLIFYING AND REBRODUCING SYSTEM FiledOct. '19, 1927 INVENTOR.

LEON F. DOUGLASS.

ATTORNEY.

Patented May 27, 1930 UNITED STATES LEON F. DOUGLASS, OF HENLO PARK,CALIFORNIA mnmr'me am) nnrnonucma sYsrEm' Application filed October 19,1927. Serial No. 227,245.

This invention relates in general to amplifying systems, and moreparticularly to audio amplifying systems adapted to operate a pluralityof loud speakers from a 6 common source. v

An object of my invention is to provide an amplifying system havingembodied therein means for producing clearer, more distinct andcomparatively stronger tones than are produced with radio apparatus nowcommonly used. v

A further object of my invention is to provide an audio amplifyingsystem having in combination with two or more sets of audio circuits,tubes and transformers, a plurality of loud speakers which are adaptedto be controlled independently of each other but are. operated from acommon source.

The accompanying drawing illustrates the circuits and arrangement of oneembodiment of my invention, but it is to be expressly understood thatthe drawing is for purposes of illustration only and is not to beconstrued as a definition of the limits ofthe invention,

reference being had to the appended claims for this purpose. 1

Referring to the drawings the letter A represents a detector tube; B and.C, a first audio tube and a second audio-tube, respectively; and D andE also a first audio tube and a second audio tube respectively. Each ofthe said tubes is ofthe kind now commonly used in radio receiving sets,and each comprises a grid 1, a plate 2 and a filament 3.

f Electrical power from a suitable source such as a set of A batteries,is carried through wires 4, and the said wires are connected by means ofconductors 5 6, 7, 8 and 9 to the filaments 3 of tubes A, B, C, D and Erespec- 'tively. I

A transformer 10 having an intermediate tap as at F has one terminal ofits primary wmding connected by wire 11 to a source of l B voltage, andthe other terminal of its primary connected by a wire 12 to the plate 2of tube. A. Its secondary winding is connected by wire 13 to the grid 1of tube B and by wire 1% to the grid 1 of tube D, while the tap F isconnected by wire 33 to the filament circuit, preferably through asuitable 23 by a wire 30 which joins wire 26.

negative bias such as a C battery. A transfOI'mQT'li has its primarywinding connected by a wire 15 to a source of B voltage and to the plate2 of tubeB by a wire 16, and its secondarg winding connected to the grid1 of tube by a wire 17 and to the ne ative terminal of a C battery by awire 18. second transformer 19 is similarly connected to the wires 15and 18, to the plate 2 of the 1D tube by a wire 20, and to the grid 1 oftube on E'by a wire 21. Two audio frequency choke coils or outputimpedances 22 and 23 are connected together to wire 26, 22 beingconnected by a wire 2 1 to the plate 2 of tube C, which wire 24 alsoconnects the said choke coil to $5 a loud speaker 25. The loud speaker25 is connected by the wire 26 to the choke coils 22 and 23, and a wire27 connects wire 26 t with a source of B voltage. The lower terminal ofchoke coil 23 is con- 7 nected to the plate 2 of tube E by a wire 28,and the said wire also is connected to a second loud speaker 29. Theloud speaker 29 is also connected to the choke coils 22 and 7 Acondenser 31 is connected to wire 12 and one of the wires 5, while thegrid 1 of tube A is connected to a grid condenser 32 shunted by a gridleak.

The arrangement of the various tubes,

transformers and their connecting wires, the

electrical energy being supplied from a single set of batteries for theoperation of the two loud speakers, makes possible the production oftones which are much clearer than those produced with ap aratus in whichone loud speaker is used. he audio tubes D and E, together with thechoke coils 22 and 23 and the transformer 19, afford suitable means forsupplying the requisite amount of electrical current from a single setof batteries for the satisfactory operation of a second loud speaker 29.The electrical energy required for the operation of-the two loudspeakers 25 and 29 is slightly more than would be 95 necessary for theoperation of a single loud speaker, but with the two loud speakers amuch greater volume can be satisfactorily produced without thedistortion. usually accompanymg the production of intensified tones by asin le loud speaker. The volume and quality 0 tone produced by each ofthe loud speakers 25- and 29 is approximately the same as that obtainedordinarily with one loud speaker, and it is not necessary to energizethe loud speakers beyond their ordinary ca acity in order to increasethe volume.

y constructing the transformers 10, 14 and 19 and/or the choke coils 22and 23 with windings of different characteristics, the two circuitssupplying current for the operation of the loud speakers 25 and 29 maybe made to conduct differentquality vibrations, thereby ermitting one ofthe loud speakers to reduce low frequency tones and the other ighfrequency tones. This featureenables the production by the combined loudspeakers of tones by the two loud speakers which are full, clear andquite similar to the original tones. As the invention is essentially anaudio amplifier and reproducer, it will be un derstood that its use isnot limited to the amplification and reproduction-of audio signalsdetected from a radio or other carrier wave, but it may be used f oroperating upon current from any source which has its output connected tothe transformer 10.

With the apparatus comprising my invention a pleasing effect maybeproduced by separating the two loud speakers. The tones produced by thetwo loud speakers can then be made to reach the car at slightlydifferent times or slightly out of phase, the result being that clear,distinct and intensified tones are received by the listener withoutdistortion or un )leasant effects.

t is therefore evident that the provision of an added circuit and thenecessary parts for supplying oscillations from a single source to aplurality of loud speakers, makes possible the production of unusualeflects with but asingle power supplying unit. It

is evident that various changes may be made in the construction andarrangement of parts without departing from the spirit of the invention,and in this connection it is desired that the appended claims define thelimits of my invention.

Having described my invention, what I claim is:

1. Apparatus of the class described comprising a source of audiofrequency energy including a transformer winding, parallel amplifyingcircuits connected to opposite ends of said winding, said amplifyingcircuits having dissimilar characteristics, an output winding having itsopposite ends con nected to said circuits, intermediate connections tosaid windings for supplying power to said circuits, and a pair of loudspeakers each receiving the output of one of said circuits.

2. Apparatus of the class described comprisinga source of audiofrequency energy including a transformer winding, parallel s ofsaidwindin said amplifying circuits having dissimilar characteristics, an

output winding having its opposite ends connected to said circuits,intermediate connections to said windings for supplying power to saidcircuits, and a pair of loud speakers each connected across a portion ofsaid output winding between one end thereof and its intermediateconnection.

3. Apparatus of the class described comprising a source of audiofrequency energy including a transformer winding having an intermediateconnection, parallel amplifying circuits connected to opposite ends ofsaid winding, said amplifying circuitshaving dissimilar characteristics,a pair of output im pedances having a connection common to one end ofeach and each having its other end connected to one of said parallelcircuits, a source of power connected between said intermediateconnection and common connection, and a loud speaker connected acrosseach of said impedances.

4. Apparatus of the class described comprising a source of audiofrequency energy including a transformer winding having an intermediateconnection, parallel amplifying circuits connected to opposite ends ofsaid winding, a pair of output impedances hav ing a connection common toone end of each and each having its other end connected to one of saidparallel circuits, :1 source of power connected between saidintermediate connections and common connection, a loud speaker connectedacross each of said impcdances,

